Solar theodolite



(No Model.) 2 Sheets-Sheet 1. J. W. HOLMES.

SOLAR THBODOLITB.

N0. 275,913. i Patented 11p-11.111883.

(No Model.) 2 Sheets-Sheet 2.

J. W. HOLMES.

SOLAR THEODOLITE.

No. 275,913t Patented Apr.17,1883.

wif/5,

UNITED STATES PATENT EEICE.

JOSEPH W. HOLMES, OF BATAVIA, NEW YORK.

SOLAR THEODOLITE.

SPECIFICATION forming` part of Letters PatentNo. 275,913, dated April 1'7, 1883.

Application filed September 12, 1882. (No model.)

To all whom it may concern:

Be it known that I, JOSEPH W. HOLMES, ot' Batavia, in the county of Genesee and State of New York, have invented new and useful lmprovements in Solar Theodolites, of which the following is a specification.

My invention relates to an apparatus combining the properties of a solar compass and theodolite or en gineers level and transit,where by the true meridian, the solar time, the suns declination,and the latitude of the place of observation can be accurately and quickly determined, and other problems of spherical trigonometry and astronomy can be readily solved.

M y present invention is an improvement ou the apparatus for which Letters Patent ot' the United States No. 205,485 were granted to me July 2, 1878, to which reference is here made for a full description thereof.

The object of my present improvements is to render said apparatus more convenient and useful and more reliable in its operation; and my invention consists of the improvements which are hereinafterfully described,and pointed out in the claims.

[n the accompanying drawings, consisting of two'sheets, Figures l and 2 are elevations of my improved apparatus, taken from opposite sides. Fig. 3 is an elevation at right angles to Fig. 1. Fig. 4 is atop plan view of the apparatus. l

Like letters of reference refer to like parts in the several figures.

A is the base upon which the standards B B are mounted, and which may consist ot' two circular plates, one revolving upon or within a graduated plate, similar to the base-plates employed in ordinary transits or theodolites.

A is a graduated compass-box, provided with a magnetic needle and secured to the base A.

C is a graduated segment, pivotcd by a horizontal shaft, a, to the standards B, and read at a vernier, D, attached to one of the standards B.

E is a plate having the form of a circle, or an are ot a circle, mounted on a pivot, b, which is journaled in the axis ofthe segment or latitude arc C, and arranged at right angles tothe axis of the segment F is a fixed circle, which may be termed the dial 7 or equatorial plate, and which is rigidly attached to the axis of the segment C.

The pivot b ot' the circle E revolves within the fixed circle F. The latter is graduated,like a compass or transit plate, to degrees and subdivisions thereof, and also to hours and fractions thereof. The circle E is provided with an are or vernier for reading the smaller subdivisions ot' the circle F.

Gis a graduated are, projecting from the face of the circle or segment E, perpendicular to its plane and called the declination-arc.77

H is an arm pivoted at d to the are G, the pivot d being located in the center from which the are Gr is described. The arm H traverses the latter with its opposite end,and is provided with a vernier for reading the arc G.

h represents projecting arms 0r bearings attached to the side ofthe arm H for holding and retaining the telescope P. vrlhe latter is provided with adjustable cross-hairs in its op tical axis, and may also be provided with stadia ormicrometer-hairs embracing the suns diameter, for more accurately centering the same, and also with a screen or colored glass, so that the sun can be viewed directly. The telescope may also have a lens at g focusing upon a silvered plate, fi.

1, s, and t are clampand tangentmovements applied to their respective arcs, O, F, and G.

Q, represents a level, attached preferably to the telescope P; but, it' desired, the level Q may be attached to the arm H, or to the circle or are E. This level is employed for adjusting the telescope for the purpose of ascertaining the time when the sun or star rises or sets, and for testing the adjustments and accuracy of thevarious parts of the instrument, and for other purposes, as hereinafter more fully explained.

The manner of using the instrument is as follows To ascertain the true solar time, level the base A, clamp the are G to the graduations representing the latitude ot' the place, and approximately iu the plane of the me ridian, clamp the arm H to the graduations of the arc G, representing the suns declination, as found in the nautical almanac, corrected for the time of day and the longitude of the place of observation, allowance being made for refraction, and adjust the zero ofthe vernier E approximately to the time, as designated by the hour and degree marks on the IOO face of the dial F. Turn the circle E in or upon the circle F, and the whole instrument, if need be, keeping the base level until the sun lisin the line of sight, when the telescope is used, or until the image of the sun falls exactly upon the plate fi. The arc C is now in the plane ot they meridian, the axis b parallel with the earths axis, and the circles F and F at right angles with the axis ofthe earth, and the time indicated by the Vernier of the circle E, reading the circle F, will be apparent or sun time, counting each degree of the arcas four minutes of time and each minute of the arc as four seconds of time. .Smaller portions of time may be read by making the Vernier E read smaller divisions of the circle F. The are C is now in the meridian of the place, and a true meridian line may be established by clamping the zero of the circle E to the twelve oclock mark ot' the circle F and settin g stakes or pins by sightingthrough the telescope. To determine what time the sun will rise or set in any latitude on any day in the year, set the latitude-arc` to the latitude of the place and the arm H to the declination of the sun. Level the instrument and bring the bubble y of the level Q to the center of the tube.

The time of sunrise will be read directly, and the time of sunset will be the reading subtracted from twclveoclock. A meridian line may also be made by the polar or a polar star at the time of greatest elongation, as follows: Turn the face of the dial-plate toward the south 3 incline it toward the north equal to the co-latitude ot' the place; set the zero of the plate E to the right or left of the zero ot' the plate F, as the elongation is east or west, equal to the polar distance of the star; keep the vertical cross-hair. upon theu star till it ceases to go east or west, as the case may be; then bring back the zero of the plate E to the zero of the plate F, and the telescope will then be parallel to the polar axis ot' the earth and in the plane of the true meridian. A meridian line may also be obtained from the polar star at any time by calculating its meridian distance and setting it off on the dial-plate F in the same manner.

rlhe adjustments of the instrument may be perfectly tested by means of the accuratelyground level-bubble upon the telescope. The intersection of the cross-hairs in the axis of the telescope and the parallelism ofthe axis of the level to theline of collim ation are accomplished in the same manner as in the ordinary Y-level. After the said adjustments are accomplished, clamp one of the zeros of the Vernier E to the zero of the plate F, the 900 mark of the segment C to the zero of its Vernier, and the zero ot' the arm H to the zero of the are G. Bring the telescope over one of the pairs of levelingscrews, and by means of these screws make thelevel horizontal. Repeat the process over the other pair of screws. Then turn the telescope halt' round-that is, till it stands over the same screws, but pointing in the opposite direction-and if the bubble does lnot remain inthe middle, correct one-halt of the error by the leveling-screws, andthe other halt' by the tangent-screw r, applied to the latitude-arc C. Continue the corrections till the bubble will remain in the middle of the tube during an entire revolution. Then turn the circle E half round. It the bubble does not remain in the center of the tube, correct one half of the error by means of the tangent-screw r, and the other halt' by means of the tangent-screw t, applied to the arc G. The zero of the Vernier D should now be set exactly to the 900'mark of the segment U and the zero ofthe Vernier on the arm H exactly to the zero of the are G.

The graduations ofthe arcs C and Gr may be compared by ixing the Vernier D to any gradnation which can be read by the arc Gr, placing the plate E to its zero and bringing the level-bubble in the center of the tube. The two readings should be the same, or one should be the complement of the other. The circle F may be compared with thearcs C and G in a similar manner.

To determine whether the axis of the plate E is exactly at right angles to the axis ofthe segment (l, before proceeding further, see it' both standards are exactly of the same height by noting if the intersection of the cross-hairs (the base A bein g leveled) will trace a plumbline. It' not, raise or lower one end of the axis a of the are C by means of adjusting-screwsp, applied to the bearings of the shaft a. Then turn the telescope parallel with the axis of the segment C, and if the level-bubble remains in thc center of the tube the axis of the plate E is at right angles to the axis of the segment C. If not, the adjustment must be made by means of the screws by which the plate F is secured to the axis of the arc G.

To see if the zero of the plate E coincides with the six oclock or 900 mark of the plate F, bring the zero of the latitude-arc C to the zero of its Vernier D and give the telescope a quarter-turn in its bearings, and bring the bubble of the level Q to the center of the tube. It' the zero of the plate E does not coincide with 900, the plate F must be made to do so.Y

The zeros of the plates E and F can be tested by setting the cross-hairs exactly on some point and then revolving the telescope half around on the axis a; fix the position of the intersection ofthe cross-hairs of this backsight; then turn the instrument half round on the axis of the base, sight to the same point and take the backsight by revolving the telescope on the axis a. lf the intersection strikes the same point as before, the telescope is exactly at right angles to the axis of the latitude-arc C. The zero of the latitude-arc may be tested by IOO IIC)

izo

bringing it to the zero of the vernier D, and if i the intersection of the cross-hairs will trace a plumb-line the adjustment is correct. The arc Gr and its Vernier may also be tested by placing the latitudearc at zero, when the dialplate will be perpendicular. Place the telescope exactly over the middle ot three pins in line, and by placing the cross-hairs over the forward one turn the telescope or circle E half round on its axis, and it the cross-hairs strike the back point the adjustment is correct.

To see it' the telescope is exactly over the center of the axis of the plate E, place the plate E in a horizontal position and the axis of the plate E exactly over the center of three pins in line, sight the cross-hairs on the forward pin, reverse the telescope in its bearings, and it' the intersection strikes the back pin the axis of the telescope is exactly over the center ofthe plate E.

lt will be seen from the foregoing that my improved instrument can be used both as a solar instrument and as a theodolite and level, and that every function ofthe instrument can be readily tested and corrected, thereby renderingtheinstrumentaccuratein every respect.

I claim -as my invention- 1. The combination of a level with the pivoted latitude-arc C, the pivoted plate E, and the declination-arc G, provided with a traversing-arm, H, substantially as and for the purpose set forth.

2. The combination, with the declination-arc G, of the arm H, traversing said arc, and a telescope, P, mounted upon the traversing-arm H, substantially as set forth.

3. The combination, with the pivoted latitude-arc C, of the pivoted plate E, the declination-arc G, provided with a traversing-arm, H, and a telescope, P, Vmounted on said traversing-arm, substantially as set forth.

4. The combination, with the declination-arc G, of the arm H, traversing said arc, and a telescope, l), and level Q, mounted upon the traversing-arm H, substantially as set forth.

5. Thecombination ofthe telescope and level 4o with the traversing-arm H, the declination-arc G, and the pivoted circle E, supporting` said are, substantially as set fort-h.

6. yThe combination ofthe telescope and level with the traversing-arm H, the declination-arc 45 Gr, the pivoted circle E, supporting said arc, and the pivoted support a, having the segment C attached thereto, substantially as set forth.

J. W. HOLMES. 

